Lead-acid storage battery capable of activation by the addition of electrolyte

ABSTRACT

A method of fashioning a lead-acid storage battery capable of being stored after completing of the battery processing and thereafter activated by the addition of electrolyte includes adding conditioning quantities of a treating agent affording certain metallic sulfates to the formation electrolyte, a rinse electrolyte or to a separate solution to obviate the necessity for removing, as by drying, all or substantially all of the electrolytes used to process the battery. Sufficient electrolyte is removed simply by draining, and the resulting battery can be stored for extended periods of time without significantly adversely affecting the performance of the activated battery.

RELATED APPLICATIONS

Mao and Sabatino, Ser. No. 377,525 now abandoned, filed July 9, 1973,for: "Method of Making a Lead-Acid Storage Battery, and the BatteryItself, Capable of Activation by the Addition of Electrolyte;" thepresent application being a continuation-in-part of Ser. No. 377,525.

Sabatino and Rao, Ser. No. 377,563 now abandoned, filed July 9, 1973,for: "Battery Vent Seal."

This invention relates to lead-acid storage batteries; and, moreparticularly, to a method for assembling such batteries which arecapable of being stored and thereafter activated simply by the additionof electrolyte, and to the resulting batteries themselves.

In recent years, considerable attention has been directed to dry chargebatteries. This type of battery is formed, the formation electrolyteremoved, the battery elements washed to remove any electrolyte residueand dried and then stored. It is ready for use merely by filling withelectrolyte. The advantages are numerous; the cost of shipping suchbatteries is substantially less than "wet" batteries in which theelectrolyte adds significantly to the weight of the battery. Also, shelflife is relatively long; and, accordingly, inventory control isfacilitated.

The full advantages of the dry charge battery have, however, not beenfully realized because of the difficulties and the expense associatedwith drying the water from the battery elements which is used to removethe electrolyte used in forming the elements. If this is not properlyaccomplished, chemical and electrochemical reactions can take placewhich adversely affect the initial battery performance. Thus, forexample, oxidation of the negative plate can occur so as to chemicallydischarge the plate thereby adversely affecting the initial performanceof the battery.

For the most part, prior techniques for removing the formationelectrolyte have been directed to thoroughly washing and drying thebattery element after formation or charging so as to prevent the batteryfrom losing its charge during storage. Thus, U.S. Pat. No. 2,880,520uses a high velocity air stream. After drying, the battery elements areinstalled into battery containers, electrically connected and a coverbonded onto the container. U.S. Pat. No. 3,314,158 discloses installingthe battery elements into the battery container and making theelectrical connections prior to the formation, washing with water anddrying steps. After the formation, a heated, nonoxidizing gas isimpinged onto the top of the battery elements.

A more recent technique, shown in U.S. Pat. No. 3,652,341, disclosesassembling the battery elements into the container and making theelectrical connections, filling the battery cells with a formingelectrolyte and then charging the battery elements. About 70 to 97weight percent of the forming acid is then removed by applying anaccelerative force, such as a centrifugal force, to the battery.

While these techniques have achieved some success, the employment ofsuch techniques adds to the manufacturing costs and lessens the economicbenefits provided by dry charge batteries. Also, these techniques arenot always successful in providing a dry charge-type battery which,after extended storage, will exhibit satisfactory performance afterbeing activated by the addition of electrolyte. In addition, thecomplexity of these techniques could cause quality control problems.

It is accordingly an object of the present invention to provide asimple, inexpensive method for making a dry charge-type storage batterycapable of being stored for extended periods of time and thereafteractivated merely by the addition of electrolyte.

Another object of this invention provides a method for making suchbatteries which obviates the necessity for using any apparatus or thelike to remove all or substantially all of the forming electrolyte fromthe battery plates or elements.

Yet another object lies in the provision of a method for making suchbatteries in which the electrolyte used in forming need only be removedby merely draining the battery container, i.e. -- a drain dry battery.

A still further object is to provide storage batteries which, afterextended storage and activation by the addition of electrolyte, aresubstantially free of internal shorts between the battery plates thatcan cause irreversible damage to the performance of the battery.

Yet another and more specific object lies in the provision of a methodfor treating a dry charge-type battery which alters the chemical andelectrochemical reactions that would otherwise take place.

Another object is to provide a method for making such batteries whichgreatly simplifies quality control.

A still further object provides a method for making such batteries thatis compatible with existing processes for forming "wet" batteries.

Yet another object of this invention lies in the provision of a methodwhich obviates the need for a washing step and the concomitantneutralization treatment necessary to allow disposal of used washsolutions to avoid possible environment problems.

A further object is to provide a method for forming lead-acid storagebatteries which may be stored without the periodic boosting chargerequired of wet storage batteries that are being stored prior to use.

Other objects and advantages of the present invention will becomeapparent from the following detailed description, and from the drawingsin which:

FIG. 1 is a schematic view of a method for making a lead-acid storagebattery in accordance with the present invention which is capable ofbeing stored for extended periods and thereafter activated merely by theaddition of electrolyte;

FIG. 2 is a graph of the solubility of lead in a sulfuric acid solutionversus the hydrogen ion concentration (pH) of the solution at 25°C. andshowing the effects of addition of varying amounts of a treating agentpursuant to the present invention on the lead solubility; and

FIG. 3 is a graph similar to FIG. 2 and illustrating the effects at atemperature of about 150°F.

While the invention is susceptible to various modifications andalternative forms, there is shown in the FIG. 1 view and will herein bedescribed in detail, the preferred embodiments. It is to be understood,however, that it is not intended to limit the invention to the specificforms disclosed. On the contrary, it is intended to cover allmodifications and alternative forms falling within the spirit and scopeof the invention as expressed in the appended claims. For example, whilethe present invention provides advantageous results when used inconnection with a method for making lead-acid storage batteries whereinthe battery is formed at the source of manufacture, shipped to thedealer without electrolyte and activated at the time of use by merelyfilling with electrolyte, it should be appreciated that the presentinvention is equally applicable to any manufacturing process whereinthere is any delay in filling the battery with acid electrolyte thatwould be sufficient to otherwise adversely affect battery performance.More specifically, the method of the present invention is compatiblewith conventional processes for assembling wet batteries. Accordingly,to simplify inventory control and obviate the need for the periodicboosting charge required by wet batteries during storage, the process ofmaking wet batteries could be interrupted after the formation step; andthe batteries conditioned in accordance with this invention prior tostorage. As desired, the thus-stored batteries could then be furtherprocessed to make fully assembled wet storage batteries. Still further,while FIG. 1 illustrates use of the present invention with a batterywherein the battery elements have been assembled and positioned in thecontainer and the appropriate electrical connections made, the presentinvention is equally applicable to use for treating the battery plateseither before or after the plates have been assembled as batteryelements.

In general, the present invention is predicated on the discovery thatthe information of lead sulfate crystals or clusters causing internalshorts between the battery plates when not all of the formingelectrolyte and wash solutions are removed from the battery can beobviated by processing the battery during manufacture with a specifictreating agent in conditioning amounts. This conditioning techniqueavoids the necessity for completely washing and drying the batteryplates or using relatively expensive techniques for removing theelectrolyte. Rather, only the electrolyte that can be removed by simplydraining the container, e.g. - by inverting and dumping, need be carriedout.

Turning now to FIG. 1, the lead-acid battery is first conventionallyassembled. As shown at station 10, the battery elements consisting of aplurality of positive and negative plates with separators disposedtherebetween are inserted into the cell compartments, and the electricalconnections are then made.

The unformed, but fully assembled, battery may then be formed (viz. -charged). Formation electrolyte is added to the battery, and a currentis applied thereto as illustrated at station 12. As is well known, theconcentration of the formation acid (typically a sulfuric acid solutionhaving a specific gravity ranging from 1.020 to 1.100) and theparticular currents applied will vary with the type of forming employedand the battery-type involved.

In a conventional dry charge process, as has been previously describedherein, the formation electrolyte is then removed, typically by dumping;and a wash solution is added. After dumping of the wash electrolyte, allthe residual electrolyte and wash solution are removed by drying.Washing in water is combined until most of the residual formation acidwith the plates and separators is diluted to water. In the process shownin U.S. Pat. No. 3,652,341, the formation electrolyte is partiallyremoved by centrifuging or the like. The amount of the residualelectrolyte is critical since an excess can cause internal shortsbetween the plates upon extended storage.

After removal of the formation electrolyte from contact with the batteryplates as shown at station 14, in accordance with one aspect of thepresent invention, the battery plates are exposed to a rinse electrolytewhich adjusts the specific gravity of the residual sulfuric acid sothat, when the completed battery is activated after storage, theelectrolyte employed for activation can have a specific gravityidentical to that utilized with a conventional dry charge battery, yetachieve the industry accepted full charge acid gravity of 1.265. Thus,the battery plates are immersed in a sulfuric acid rinse solution havinga specific gravity sufficiently higher than that of the formationelectrolyte to raise the specific gravity of the residual sulfuric acidsolution remaining on the battery plates (after draining the rinsesolution) to the desired level. Typically, the rinse solution will havea specific gravity of about 1.200 to 1.400, the specific level dependingprincipally on the battery size and capacity. As is shown in FIG. 1, therinse step can be effected merely by filling the container (station 16)with the rinse solution via the vent openings. After allowing sufficienttime for the rinse acid to mix with the residual formation acid in theplates, sufficient removal of excess rinse solution is accomplishedsimply by draining the battery, viz. - by inverting the container anddumping, as indicated at station 18.

It should be appreciated that, while the rinse step provides a definiteadvantage in allowing use of the identical electrolyte employed foractivation of conventional dry charge batteries, this step is optionaland can be eliminated if desired. Elimination will, however, of course,necessitate the use of an activation electrolyte with a differentspecific gravity than used for conventional dry charge batteries,typically higher, if the advantage of using the conventional activationelectrolyte is to be realized.

In accordance with a preferred embodiment of the present invention, thetreating or conditioning step can be advantageously carried out byincorporation of the treating or conditioning agent in the rinsesolution. The treating agent should be added in an amount of from about0.05 to about 5 per cent (anhydrous metallic sulfate), based upon theweight of the rinse acid solution.

The conditioning agents, pursuant to this invention, comprises a metalsulfate or other metal compound which will yield the sulfate in anaqueous sulfuric acid solution (i.e. - will react in the solution toform the metal sulfate) and which metal sulfates or other compounds are:(1) sufficiently soluble in aqueous sulfuric acid solutions to providethe requisite conditioning quantities of the metal sulfate, (2) are notsubstantially harmful to either the battery components or to theperformance of the battery in use (e.g. - not cause corrosion of theelements as would sodium acetate, gassing or the undesirable effects ofthe sulfates of iron, nickel, manganese, bismuth, platinum, mercury orchromium) and (3) not susceptible to produce a lead salt that wouldlikely precipitate in sufficient amounts which would significantlyreduce the porosity of the battery plates.

More particularly, the metallic sulfates of sodium (and its bisulfate),potassium, lithium, magnesium, cadmium, zinc and aluminum have beenfound to be useful. While each of these materials have been found to besuitable to achieve the conditioning of the batteries in accordance withthis invention, it should be appreciated that the advantages derived mayvary somewhat depending on the specific material used and the amountemployed. From the economic standpoint, sodium sulfate and also zincsulfate are preferred. Other sulfates which could be employed includethe sulfates of silver and cobalt. Still other sulfates that may be usedare the following: BeSO₄, Ce₂ (SO₄)₂, In₂ (SO₄)₃, La₂ (SO₄)₃, SnSO₄, Tl₂SO₄, Zr(SO₄)₂ and Rb₂ SO₄.

Suitable metallic compounds which afford the metallic sulfates in anaqueous sulfuric acid solution and meet the criteria previously setforth include the corresponding hydroxides and oxides. For example, theaddition of sodium hydroxide, potassium hydroxide and zinc oxide to formthe metallic sulfate treating agent have been found effective to preventthe development of internal shorts within the elements. It is preferredto use the corresponding sulfates since the rates of self-discharge ofplates treated with such hydroxides and oxides appears to be slightlyvariant.

In addition to these other metallic compounds, the hydrated sulfates(i.e. - having waters of crystallization associated therewith) may alsobe advantageously employed. However, in either instance, the amount ofthe material used as the treating agent should be adjusted to provide anamount corresponding to the quantity required to afford in the rinsesolution the amount of the metal resulting from the use of from about0.05 to about 5.0 per cent by weight of the anhydrous metallic sulfate.

If desired, mixtures of different materials can suitably comprise thetreating agent. Moreover, while certain compounds have been describedherein as being unsuitable to function as the treating agent, it shouldof course be appreciated that these unsuitable materials can betolerated, within certain limits, so long as their undesirable effectsare masked by the presence of the useful treating agent.

To achieve optimum results, the rinse solution containing the treatingagent should be allowed to condition the battery plates so thatdiffusion into the wet battery plates and separators results. Thisconditioning can be accomplished, for example, by merely allowing therinse solution to stand in contact with the plates for about 10 minutesor even longer. This soaking is effective to allow the treating agentsolution to diffuse and mix with the residual formation electrolyte inthe plates. Alternatively, the conditioning may be accomplished bymechanically mixing the rinse solution while it is in contact with thebattery plates. Any conventional mechanical mixing means may beadvantageously utilized.

Completion of the processing then involves sealing the battery to atleast substantially prevent the ingress of air. As illustrated in FIG.1, this may be carried out by sealing the cover vent openings withsuitable closures. The sealed battery is shown at station 20 and may nowbe stored for extended periods of time. However, while completelysealing the drain dry battery of the present invention may be suitable,it is preferred to only seal the battery sufficiently so that theingress of air is just substantially prevented. Thus, because the draindry batteries do retain residual electrolyte, there is some slightinternal generation of gases such as hydrogen caused by self-dischargeof the negative active materials during extended storage. If thebatteries are totally sealed to protect against oxidation, there can besome bulging of the containers as a result of hydrogen and other gasbuild-up. In addition, this pressure build-up can result in ejection ofthe vent caps. If this occurs and the vent caps are not timely replaced,massive self-discharge of the negative plates can result, thus renderingthe battery unusable immediately upon addition of electrolyte until thebattery is fully recharged. It is therefore preferred to seal thebattery in such a fashion that the ingress of air is substantiallyprevented while permitting the gaseous atmosphere within the battery,after a slight pressure build-up, to be vented from the battery. Aparticularly desirable means of accomplishing the sealing so as tosubstantially prevent the ingress of air is described and claimed in theco-pending applications of Sabatino and Rao, entitled "Battery VentSeal", assigned to the assignee of this invention, and referred tohereinbefore, wherein the seals for the battery vent openings areprovided with a means communicating with the atmosphere such as circularapertures having diameters of from about 0.0005 to 0.006 inch.

In accordance with another embodiment of the present invention, theconditioning agent can be applied during the formation step. Thus, as isillustrated in FIG. 1, the conditioning or treating agent can beincluded in the formation acid added at station 12. It has been foundsuitable in this embodiment to include no more than about 2 per cent orless by weight of the formation acid. Further processing then involvesdraining the formation acid and rinsing, if desired, (with or withoutaddition of further treating agent), followed by draining the rinsesolution and then sealing the battery as before.

A still further embodiment involves applying the conditioning agent in aseparate step following either draining of the formation acid or, ifused, the rinse solution, FIG. 1 showing the latter mode (station 22).The solution containing the conditioning agent is then drained, and thebattery is thereafter sealed as before. The conditioning agent cansuitably be added in a solvent such as, for example, water in an amountaffording from about 0.05 to about 10.0 per cent anhydrous metalsulfate, based upon the weight of the solvent. Also, the conditioningagent may be included in an aqueous sulfuric acid solution, desirablyhaving the same specific gravity as the rinse acid so as to avoidreducing the specific gravity of the residual electrolyte on the batteryplates.

When the conditioning agent is added to either the formation electrolyteor in a solvent in a separate step, the treating agent can consist ofany of the metallic sulfates or other compounds described in connectionwith the rinse acid embodiment so long as the criteria set forth thereinare observed. Also, as in the rinse acid embodiment, optimum results areachieved by allowing the plates to be conditioned as described therein.

Regardless of the process step in which the treating acid is added, itis important that the amount be sufficient to provide the minimumconditioning required, i.e., that amount sufficient to substantiallyprevent internal shorts between the battery plates that causeirreversible damage to the performance of the battery. The amountnecessary to achieve this effect will depend upon the step in which thetreating agent is added and the amount of dilution which results fromthe rinse acid or other solutions added. Irrespective of when thetreating agent is added, the amount is adequate so long as the residualtreating agent upon storage of the formed battery is at least about 0.02per cent, based upon the total weight of the residual electrolyte in thebattery. The exact amount may also vary somewhat depending upon thespecific treating agent being utilized; for example, when aluminumsulfate is added to the rinse acid, it should be present in an amount ofat least about 0.1% by weight of the rinse acid.

Increased amounts of treating agent, well above the minimum (i.e., up toabout 5% by weight of the solution), can also be suitably used. However,the amount employed should not be so excessive as to significantlyadversely affect the battery performance. The battery reserve capacityand cold preformance can particularly be affected by excessive amountsof treating agent. Moreover, if the treating agent is added with theformation acid, excessive amounts can impair the ability to reach thedesired end-of-charge voltage. The maximum tolerable amount can varysomewhat, depending upon the specific treating agent employed.

The following examples are illustrative, but not in limitation of thepresent invention. Unless otherwise specified, all percentages are byweight. The high temperature storage carried out in the examples wasused to simulate room temperature conditions that would occur over alonger period of time. The sulfates used as the treating agent wereanhydrous unless otherwise specified.

EXAMPLE 1

A Group 24 battery (53 Amp. Hr. capacity) was formed, and theconditioning agent was thereafter applied in varying weight percentages,either to the rinse acid or in a separate step after removal of theformation acid from the battery by inverting and dumping. Mechanicalmixing was employed in all cases.

After the conditioning, in all cases, the cover vent openings weresealed; and the batteries were stored at 150°F. for 35 days. Followingstorage, the cover vent openings were unsealed, electrolyte added, aboosting charge given and the battery performance evaluated.

The results are shown in Table I:

                                      Table 1                                     __________________________________________________________________________              5 Amp Boosting Following                                                                      20 Hour Capacities (Hrs.)                                     Activation with 1.300 Acid                                                                    (Numbers in Parentheses                                                                            0°F BCI                                                                Performance                              Time Into                                                                            End of   are Internal Resistance (mΩ))                                                                           Time to             Battery Number                                                                          Boosting                                                                             Charging 1st    2nd    3rd    312 Amp Discharge                                                                        7.2V                and Treatment                                                                           (Mins) Voltage (V)                                                                            Cycle  Cycle  Cycle  5 Second                                                                                 Seconds             __________________________________________________________________________    (1)                                                                              2.0%   221    16.72    22.05  21.6   20.4   7.73       61.7                   Na.sub.2 SO.sub.4 in   (10.8mΩ)                                                                       (10.8mΩ)                                                                       (10.8mΩ)                           water                                                                      (2)                                                                              2.0%   300    16.05    21.45  21.5   20.6                                     Na.sub.2 SO.sub.4 in   (11.5mΩ)                                                                       (11.42mΩ)                                                                      (11.3mΩ)                                                                       7.63       58.1                   rinse acid                                                                 (3)                                                                              10.0%  221    16.68    22.60  21.9   20.77                                    Na.sub.2 SO.sub.4 in   (10.8mΩ)                                                                       (10.8mΩ)                                                                       10.75mΩ)                                                                       7.74       60.9                   water                                                                      (4)                                                                              10.0%  300    15.76    22.00  21.6   20.30                                    Na.sub.2 SO.sub.4 in   (11.3mΩ)                                                                       (11.15mΩ)                                                                      (11.1 mΩ)                                                                      7.63       53.3                   rinse                                                                         acid                                                                       __________________________________________________________________________

EXAMPLE 2

Example 1 was repeated, except that the boosting step was varied, andthe formed batteries were stored at 110°F. for 61 days.

The results are shown in Table II:

                                      Table II                                    __________________________________________________________________________              5 Amp Boosting Following                                                                      20 Hour Capacities (Hrs.)                                     Activation with 1.300 Acid                                                                    (Numbers in Parentheses                                                                            0°F BCI                                                                Performance                              Time into                                                                            End of   are Internal Resistance (mΩ))                                                                           Time to             Battery Number                                                                          Boosting                                                                             Charging 1st    2nd    3rd    312 Amp Discharge                                                                        7.2V                and Treatment                                                                           (Mins) Voltage (V)                                                                            Cycle  Cycle  Cycle  5 Second                                                                                 Seconds             __________________________________________________________________________    (5)                                                                              2.0%   180    16.59    21.2   21.3   20.0   7.53       45.0                   Na.sub.2 SO.sub.4 in   (11.9mΩ)                                                                       (11.8mΩ)                                                                       (11.7mΩ)                           water                                                                      (6)                                                                              2.0%   240    16.43    19.0   19.7   18.35  7.43       30.0                   Na.sub.2 SO.sub.4 in   (12.5mΩ)                                                                       12.5mΩ)                                                                        (12.3mΩ)                           rinse                                                                         acid                                                                       (7)                                                                              10.0%  240    16.54    21.2   21.0   19.7   7.53       45.0                   Na.sub.2 SO.sub.4 in   (11.7mΩ)                                                                       (12.0mΩ)                                                                       (12.0mΩ)                           water                                                                      (8)                                                                              10.0%  270    15.80    17.7   17.7   15.8   7.26       20.0                   Na.sub.2 SO.sub.4 in   (11.8mΩ)                                                                       (12.2mΩ)                                                                       (12.0mΩ)                           rinse                                                                         acid                                                                       __________________________________________________________________________

EXAMPLE 3

Group 24 plastic batteries (62 Amp. Hr.) were formed with an sulfuricacid aqueous formation, and the conditioning agent was added to eitherthe formation acid or to the rinse acid. In all cases, after invertingand dumping to remove the rinse acid, the cover vent openings weresealed; and the batteries were then stored at 110°F. for 21 days.

After opening the cover vent openings, electrolyte was added, and thebatteries evaluated. The results are shown in Table III:

                                      Table III                                   __________________________________________________________________________                   30°F Activation                                                                   25A    0°F Performance                                                                  -20°F                                                                            25 Amp Reserve                          290 Amp Discharge                                                                        Reserve                                                                              387 Amp Discharge                                                                       310 Amp Discharge                                                                       Capacity Minutes         Battery Number 15 Sec. V.                                                                          Time to                                                                            Capacity                                                                             5 Sec. V.                                                                          Time to                                                                            5 Sec. V.                                                                          Time to                       and Treatment  Volts 7.2V-Sec.                                                                          Minutes                                                                              Volts                                                                              7.2V-Sec.                                                                          Volts                                                                              7.2V-Sec.                                                                          1 Cycle                                                                            2                   __________________________________________________________________________                                                              Cycle               1. Formed in a sulfuric                                                                      8.53   83.0                                                                               95.0  7.21 6.6  7.24 7.0   93.0                                                                               92.0                  acid solution contain-                                                        ing 2.0% Na.sub.2 SO.sub.4.                                                2. Formed in a sulfuric                                                                      8.71  113.0                                                                              116.0  7.40 41   7.72 50   110.0                                                                              116.0                  acid solution contain-                                                        ing 0.5% Na.sub.2 SO.sub.4.                                                3. Treated with a                                                                            8.61   95.0                                                                              117.0  7.44 52   7.54 34   118.0                                                                              117.0                  rinse acid contain-                                                           ing 2.0% Na.sub.2 SO.sub.4.                                                4. Treated with a                                                                            8.66  102.0                                                                              120.0  7.47 41   7.39 35   119.0                                                                              110.0                  rinse acid containing                                                         0.5% Na.sub.2 SO.sub.4.                                                    Specification 15 Sec. V.         Specification                                                                           Specification                                                                           Reserve Capacity         7.2 Volts                        30 Sec. V.-7.2V                                                                         30 Sec. V.-7.2V                                                                         Rating--90               __________________________________________________________________________                                                         min.                 

EXAMPLE 4

Group 24 batteries (62 Amp. Hr.) were formed using an aqueous sulfuricacid solution. Sodium sulfate in varying quantities was added to theformation acid in each run, and the subsequent processing steps werealso varied. Thus, in Run Nos. 2 and 3, after draining of the batteries,these were evacuated at 150°F. for 45 minutes. Also, in Run No. 6, afterapplication of 10 amps. for 7 minutes to the drained batteries, anevacuation at 155°F. for 45 minutes was carried out. Further, afterdraining of the formation acid in Run Nos. 4-6, a rinse with aqueoussulfuric acid solution was carried out.

The batteries were then, after sealing of the cover vent openings,stored at 110°F. After varying numbers of days, the cover vent openingswere unsealed and batteries activated by addition of electrolyte andevaluated. The results are shown in Table IV:

                                      Table IV                                    __________________________________________________________________________                     30° Activation                                                                         0°F Cold Test                                                                       -20°F Cold Test                           Dis-                                                                              15  Time                                                                             20 Hr.                                                                             R.C.*                                                                             30Sec.V                                                                            Time to                                                                           10Sec.V.                                                                           Time to                                     charge                                                                            Sec.V.                                                                            to Capacity                                                                           Min.     7.2V     7.2V R.C.                                                                             R.C.               Run         Storage                                                                            Rate    7.2V                                                                             Min.          Sec.                                                                              Sec. Min. Min.                  No.                                                                              Treatment                                                                              (Days)                                                                             Amps    Sec.                                                 __________________________________________________________________________    1  2.0% Na.sub.2 SO.sub.4                                                                 21   290 0   0  1105 103 7.15 26  6.93  7   106                                                                              102                   in formation                                                                           21              1020 102 7.09 19  7.13 21   105                                                                              95                    acid                                                                                   42   290 0   0  1184  87 7.3  40  7.18 28   103                                                                              106                2  0.5% Na.sub.2 SO.sub.4                                                                 21   290 0   0  1103 110 7.2  30  7.13 21   113                                                                              101                   in formation                                                                           21              1185 115 7.27 42  7.33 50   115                                                                              105                   acid with evacu-                                                              ation                                                                      3  2.0% Na.sub.2 SO.sub.4                                                                 21   290 0   0  1125 109 7.03 10  6.9   4   110                                                                              97                    in formation                                                                           42   290 0   0  1205  85 --   15  7.12 21   105                                                                              106                acid with   Cut open after being tipped over during 84 days storage at                    110°F -- negative and                                      evacuation  positive plates partially discharged; no crystal growth,                      small amount of sulfate                                                       on positive plates                                                4  2.0% Na.sub.2 SO.sub.4                                                                 21   290 8.53                                                                              83  960  95 6.66  6  6.75  7   92 92                    in formation                                                                           42   290 8.31                                                                              80 1192  87 --   10  6.49  0   98 99                    acid with rinse                                                                        85   266 7.36                                                                              25 1062  89 --    7  --    2   98 98                 5  0.5% Na.sub.2 SO.sub.4                                                                 21   290 8.71                                                                              113                                                                              1055 116 7.27 41  7.42 50   110                                                                              116                   in formation                                                                           42   290 8.42                                                                              89 1205 102 7.44 65  7.56 48   105                                                                              111                   acid with                                                                              68   266 --  10 1135 107 7.50 65  7.59 42   106                                                                              110                   rinse                                                                      6  2.0% Na.sub.2 SO.sub.4                                                                 21   290 8.59                                                                              74  915  90 6.77  7  6.62  3   92 90                    in formation                                                                           42   290 8.28                                                                              63 1105  83 --   10  6.62  5   93 95                    acid with rinse                                                                        95   266 7.63                                                                              47 1055                                                 and evacuation                                                             __________________________________________________________________________     *R.C. = Reserve Capacity                                                 

EXAMPLE 5

Group 24 batteries (62 Amp. Hr.) were formed using an aqueous sulfuricacid solution. An aqueous sulfuric acid rinse solution was used in eachrun, and sodium sulfate in varying quantities was added either to theformation acid or the rinse solution.

The subsequent processing steps were also varied. In Run Nos. 10 and 11,after mechanically mixing the rinse acid solution in the batteries,these batteries were heated in a water bath maintained at 120°F. for 30minutes, a current of 10 amps. applied for 7 minutes and then evacuatedat 150°F. for 45 minutes. In Run No. 7, after draining the rinsesolution, a current of 10 amps. was applied for 7 minutes, followed byevacuation at 155°F. for 45 minutes.

After the final processing step (evacuation in Run Nos. 7, 10 and 11 anddraining of the rinse solution in Runs 8 and 9), the cover vent openingswere sealed; and the batteries stored at 110°F. After varying number ofdays, the cover vent openings were unsealed, the batteries activated byaddition of electrolyte and evaluated. The results are set forth inTable V:

                                      Table V                                     __________________________________________________________________________    Run                                                                              Treatment                                                                           Storage                                                                            30°F Activation                                                                            0°F Cold Test                                                                      -20°F Cold Test          No.      (Days)                                                                             Dis-                                                                              15   Time                                                                             20 Hr.                                                                             R.C.                                                                             30Sec.V                                                                             Time to                                                                             30Sec.V                                                                             Time to                                 charge                                                                            Sec.V                                                                              to Capacity                                                                           Min.     7.2V Sec    7.2V R.C.                                                                             R.C.                            Rate     7.2V                                                                             Min.                      Sec. Min.                                                                             Min.                            Amps     Sec.                                                   __________________________________________________________________________     7*                                                                              Formation                                                                           21   290 8.80 121                                                                              1142 115                                                                              7.35  55    7.5   41   118                                                                              115                  acid con-                                                                           42   290 8.41 82 1248 104                                                                              7.37  55    7.44  48   113                                                                              114                  taining                                                                             82   266 7.19 15 --   107                                                                              7.43  55    7.52  47   114                                                                              111                  0.5%                                                                          Na.sub.2 SO.sub.4                                                          8  Rinse 21   290 8.61 95  900 117                                                                              7.35  55    7.29  35   118                                                                              117                  acid con-                                                                           42   290 8.39 78 1189 102                                                                              7.43  65    7.1   49   111                                                                              112                  taining                                                                             68   266 7.69 -- 1106 113                                                                              7.53  65    7.43  35   112                                                                              110                  2.0%                                                                          Na.sub.2 SO.sub.4                                                          9  Rinse 21   290 8.66 102                                                                              1080 120                                                                              7.29  42    7.22  35   119                                                                              110                  acid con-                                                                           42   290 8.27 53 1220 123                                                                              7.40  60    7.47  50   116                                                                              110                  taining                                                                             68   266 7.35 23 1154 107                                                                              7.48  59    7.43  37   114                                                                              112                  0.5%                                                                          Na.sub.2 SO.sub.4                                                          10*                                                                              Rinse 21   290 8.83 113                                                                              1156 124                                                                              Bad terminal                                   acid con-                      cut open                                    taining  42   290 8.40 70 1270 105                                                                              7.48  65    7.59  58   112                                                                              114               2.0%     68   266 7.46 -- 1118 113                                                                              7.49  62    7.48  39   112                                                                              110               Na.sub.2 SO.sub.4 at 5 Sec.                                                                     would not                                                                     accept current                                              11*                                                                              Rinse 21   290 3.85 105                                                                              1131 120                                                                              7.32  50    7.39  40   114                                                                              114                  acid con-                                                                           42   290 8.32 60 1245 105                                                                              7.47  65    7.5   47   115                                                                              118                  taining                                                                             82   290 0.98 -- 1177 108                                                                              7.52  64    7.51  40   115                                                                              112               0.5%              at 5 Seconds                                                Na.sub.2 SO.sub.4 would not                                                                     accept                                                                        current                                                     __________________________________________________________________________     *evacuation step included                                                

EXAMPLE 6

Group 24 batteries (62 Amp. Hr.), a Group 24 battery (53 Amp. Hr.) and aGroup 22 battery (53 Amp. Hr.), all fully assembled with the coversbonded to the containers, were filled with an aqueous sulfuric acidformation electrolyte having a specific gravity of 1.060. The batterieswere filled through the cover vent openings to the bottom of the ventopenings.

The batteries were then charged using D. C. current with the currentlevel depending upon the battery capacity (viz. - 53 Amp. Hr. - 7amps;62 Amp. Hr. - 8 amps). This was continued for about 12 hours, afterwhich the current level was dropped (53 Amp. Hr. - 4 amps; 62 Amp. Hr. -5). The reduced current level was maintained for about 6 hours, andforming was completed by further reducing the current to 3 amps forabout 1 to 3 hours.

After completion of the formation, the formation acid was drained fromthe batteries. An sulfuric acid aqueous rinse solution was then added,filling to about the bottom of the cover vent openings. About 0.5percent anhydrous sodium sulfate, based upon the weight of the rinsesolution, was added thereto; and conditioning was carried out by mixingor soaking.

The rinse solution was then dumped by inverting the batteries anddraining. The cover vent openings were sealed; and the batteries storedat 110°F. for a varying number of days. After storage, the cover ventopenings were unsealed; and the batteries activated by the addition ofelectrolyte and thereafter evaluated.

The results are shown in Table VI:

                                      Table VI                                    __________________________________________________________________________    Bat-                                                                             Battery Type                                                                         No. of                                                                            30°F. Activation                                                                   25 AMP                                                                            0°F Performance                                                                    -20°F. Performance           tery                                                                             and Process                                                                          Days                                                                              Discharge Rate-                                                                           Reserve                                                                           Discharge Rate -                                                                          Discharge Rate                                                                            25 AMP Reserve          No.                                                                              Description                                                                          Stored                                                                            290 AMPS    Capacity                                                                          387 AMPS    310 AMPS    Capacity                __________________________________________________________________________                                                          Mins.                                 5Sec.                                                                             15SEc.                                                                            Time                                                                              Mins.                                                                             5 Sec.                                                                            30Sec.                                                                            Time                                                                              5Sec.                                                                             30Sec.                                                                            Time                                                                              Cycle                                                                              Cycle 2                          V.  V.  to 7.2V     V.  to 7.2V.                                                                          V.  V.  to 7.2V                                           Sec.            Sec.        Sec.                        __________________________________________________________________________    1  Group 24                                                                             68  7.78                                                                              7.76                                                                              53.0                                                                              128.0                                                                             7.39                                                                              7.31                                                                              40.0                                                                              7.35                                                                              7.20                                                                              --  131.0                                                                              132.0                 (62A.H)                                                                       acid-mech-                                                                    anical mixing                                                              2  Group 24                                                                             94  7.86                                                                              7.85                                                                              67.0                                                                              126.0                                                                             7.38                                                                              7.27                                                                              40.0                                                                              7.39                                                                              7.27                                                                              37.0                                                                              120.0                                                                              125.0                 (62A.H.)                                                                      1.200 rinse                                                                   acid mech-                                                                    anical mixing                                                              3  Group 24                                                                             70  7.63                                                                              7.61                                                                              69.0                                                                              119.0                                                                             7.33                                                                              7.20                                                                              32.0                                                                              7.55                                                                              7.29                                                                              40.0                                                                              119.0                                                                              115.0                 (62A.H.)*                                                                     1.265 rinse                                                                   acid-mech-                                                                    anical mixing                                                               4 Group 24   Discharge at 211 Amps.                                                                        Discharge at 281 Amps.                                                                    Discharge at 225 Amps.              (53A.H.)* 71  8.47                                                                              8.42                                                                              54.0                                                                               80.0                                                                             7.70                                                                              7.57                                                                              65.0                                                                              7.42                                                                              7.28                                                                              38.0                                                                               93.0                                                                               91.0              1.280 rinse                                                                   acid - soak                                                                   20 mins.                                                                      5  Group 22   Discharge at 211 Amps.                                                                        Discharge at 281 Amps.                                                                    Discharge at 225 Amps.              (53A.H.)* 86  7.99                                                                              7.95                                                                              61.0                                                                               82.0                                                                             7.63                                                                              7.50                                                                              61.0                                                                              7.40                                                                              7.30                                                                              62.0                                                                               82.0                                                                               83.0              1.280 rinse                                                                   acid - soak                                                                   10 mins.                                                                      __________________________________________________________________________     Specifications:                                                               (1) 30°F Activation and 0°F and -20°F performance:       7.2 V. at 15 Sec.                                                             (2) Reserve capacity: 53 A.H.--70 min.; 62 A.H.--90 min.                      *using circular vent seals having a 0.001 inch diameter                  

EXAMPLE 7

The effect of the addition of varying amounts of sodium sulfate upon thesolubility of lead in any form (e.g. - lead sulfate) in sulfuric acidsolutions of varying pH is shown in FIGS. 2 and 3.

Two liters of each of the various solutions were prepared in Erlenmeyerflasks. One liter of each solution was tested at room temperature(77°F.) and the other at about 150°F. as will hereinafter be described.

To form the solutions having a pH in the range of about 1 or so, varyingamounts of sulfuric acid and sodium sulfate were added to distilledwater, after which freshly precipitated lead sulfate was added inexcess. For solutions having a pH of about 5 or more, varying amounts ofsodium sulfate and excess freshly precipitated lead sulfate were addedto distilled water.

The solutions were initially heated at temperatures 15° to 30°F. higherthan the nominal temperatures desired (viz. - 77°F. or 150°F.) and wereperiodically stirred in contact with the added, excess, solid leadsulfate to approach saturation at the higher temperatures for about 8hours and then allowed to stand at the nominal temperature for about 64hours.

The solubility of the lead in the solutions at 77°F. was carried out byfiltering the solution using a fritted Buchner funnel, and the lead inthe resulting saturated solution is determined by atomic absorption. Thequantity of lead in the 150°F. solutions was determined by first heatingthe flask and Buchner funnel to 150°F. and filtering the solution intothe flask. It was observed that some cooling had occurred, and EDTA wasadded to re-solubilize the precipitated lead compounds; however, someinherent error may well be involved. The amount of lead in solution inthe resulting filtered solution was then measured by atomic absorption.

The pH of the various solutions was determined at room temperature.

As can be seen from FIGS. 2 and 3, the addition of sodium sulfate to thesulfuric acid solutions significantly depresses the solubility of lead(as lead sulfate and other lead compounds) in the solutions. It istheorized that the lessening of these lead compounds in solution mayaccount, at least in part, for the results achieved by this inventiondue to a lessening of the likelihood of precipitation of lead sulfateand the like and the concomitant crystal growth that can eventually leadto internal shorts in a battery if the crystal growth bridges betweenadjacent plates.

EXAMPLE 8

A number of cells (53 Amp. Hr. automotive-type elements) were fullyassembled, conventionally formed with a sulfuric acid aqueous solution,and different treating or conditioning agents were added to the rinsesolution. After inverting and dumping to remove the rinse acid, thecells were substantially sealed with vent seals having about a 1 milaperture and stored for 93 days at 110°F.

After opening, the cells were visually evaluated; the results are shownin Table VII:

                                      Table VII                                   __________________________________________________________________________    Type and Concentration of                                                                    Visual Observation of Elements                                                                      Condition of Separator                     Treating Agent                                                                             (Positive and Negative Plates)                                 __________________________________________________________________________    0.1% Al.sub.2 (SO.sub.4).sub.3                                                               Growth of large sulfate crystals on                                                                 Holes in separators --                                  positive plates. Shorted cells                                                                      short through separator                  0.25% Al.sub.2 (SO.sub.4).sub.3                                                              No large sulfate crystals on the                                                                    Good                                                    surface of positive plate                                      0.4% Al.sub.2 (SO.sub.4).sub.3                                                               No large sulfate crystals on the                                                                    Good                                                    surface of positive plate                                      0.2% CdSO.sub.4                                                                              Small sulfate crystals on the                                                                       Good                                                    surface of positive plate                                      0.5% CdSO.sub.4                                                                              Positive plates in excellent condition                                                              Good                                                    without large sulfate crystal growth                           0.8% CdSO.sub.4                                                                              Positive plates in excellent condition                                                              Very good                                               without large sulfate crystal growth                           0.1% K.sub.2 SO.sub.4                                                                        Positive plates in very good condition                                                              Good                                                    without large sulfate crystal growth                           0.2% K.sub.2 SO.sub.4                                                                        Some small sulfate crystals. (Would                                                                 Good                                                    not have caused damage)                                        0.4% K.sub.2 SO.sub.4                                                                        Positive plates in excellent condition                                                              Very good                                               without sulfate crystal growth                                 0.1% Li.sub.2 SO.sub.4                                                                       Positive plates in excellent condition                                                              Excellent                                0.5% Li.sub.2 SO.sub.4                                                                       without sulfate crystal growth                                 0.8% Li.sub.2 SO.sub.4                                                        0.1% MgSO.sub.4                                                                              Positive plates exhibit small sulfate                                                               Good                                                    growth                                                         0.4% MgSO.sub.4                                                                              Some sulfate crystals on the positive                                                               Good                                                    plate                                                          0.6% MgSO.sub.4                                                                              Positive plates in good condition without                                                           Good                                                    sulfate crystal growth                                         0.1% ZnSO.sub.4                                                                              Positive plates in excellent condition                                                              Excellent                                0.2% ZnSO.sub.4                                                                              without sulfate crystal growth                                 0.4% ZnSO.sub.4                                                                              Positive plates in good condition without                                                           Good                                                    sulfate crystal growth                                         0.5% Na.sub.2 SO.sub.4                                                                       Positive plates in good condition without                                                           Good                                                    sulfate crystal growth                                         No additive    Positive plates exhibit large sulfate                                                               Good                                                    growth at frame bars. Such growth can                                         cause shorts                                                   __________________________________________________________________________

EXAMPLE 9

Group 24 plastic batteries (62 Amp. Hr.) were formed with a sulfuricacid aqueous 20 hr. formation, and various amounts and types of treatingagents were added to the rinse acid. After inverting and dumping toremove the rinse acid, the cover vent openings were substantially sealedusing vent seals having a channel vent opening therein; and thebatteries were stored at 110°F. for 104 days or more.

After opening the cover vent openings, electrolyte was added; and thebatteries were evaluated. The results are shown in Table VIII:

                                      Table VIII                                  __________________________________________________________________________    Type and    Open                                                              Concentra-                                                                           No. of                                                                             Circuit                                                           tion of                                                                              Days of                                                                            Voltage                                                                            30°F Activation                                                                           0°F Cold Performance               Metallic                                                                             Storage                                                                            Prior                                                                              266 AMP Discharge  355 AMP Discharge                         Sulfate in                                                                           at   to Acti-         time to           Time to                                                                              Reserve Capacity        Rinse Acid                                                                           110°F.                                                                      vation                                                                             5sec.V.                                                                             15sec.V.                                                                            7.2V sec.                                                                            5sec.V.                                                                             30sec.                                                                             7.2V sec.                                                                            Minutes                 __________________________________________________________________________    0.5% CdSO.sub.4                                                                      130  6.08 Sample used for Scanning                                                                         electron Microscope Examination           0.5% CdSO.sub.4                                                                      137  5.53 7.98  7.95  64.0   7.70  7.51 63     119                     0.4% K.sub.2 SO.sub.4                                                                144  9.08                                                              0.4% K.sub.2 SO.sub.4                                                                144  7.27                                                              0.4% ZnSO.sub.4                                                                      116  7.59 8.29  8.29  88.0   7.64  7.49 61     123                     0.4% ZnSO.sub.4                                                                      130  8.95 Sample used for Scanning                                                                         electron Microscopic                                                                            118mination             0.4% Al.sub.2 (SO.sub.4).sub.3                                                       129  5.85 8.22  8.19  58.0   7.76  7.58 70                             0.4% Al.sub.2 (SO.sub.4).sub.3                                                       110  7.17 8.50  8.51  77.0   7.58  7.41 60     124                     0.4% MgSO.sub.4                                                                      135  4.61 7.57  7.48  35.0   7.69  7.48 63     118                     0.4% MgSO.sub.4                                                                      131  5.77 8.33  8.30  83.0   7.64  7.45 58     121                     0.5% Li.sub.2 SO.sub.4                                                               129  6.19 8.05  8.01  68.0   7.62  7.41 55     120                     0.5% Li.sub.2 SO.sub.4                                                               114  7.43 8.09  8.05  71.0   7.57  7.42 62     114                     0.5% Na.sub.2 SO.sub.4                                                               104  8.52 8.54  8.51  71.0   7.71  7.56 70     115                                      Specification      Specification     Reserve Capacity                         15sec.V.           30sec.V.          Rating - 90 min.                         7.2 Volts          7.2 Volts                                 __________________________________________________________________________

EXAMPLE 10

Group 24 plastic batteries (62 Amp. Hr.) were formed using a sulfuricacid aqueous 20 hr. formation, and various amounts and types of metallichydroxides and oxides, affording the corresponding sulfate upon additionto an aqueous sulfuric acid solution, were added to the rinse acid.After inverting and dumping to remove the rinse acid, the cover ventopenings were substantially sealed as described in Example 9; and thebatteries were stored at 110°F. for 82 days or more.

After opening the cover vent openings, electrolyte was added; and thebatteries were evaluated. The results are shown in Table IX:

                                      Table IX                                    __________________________________________________________________________    Type of    Open                                                               Additive   Circuit                                                            and Con-                                                                            No. of                                                                             Voltage                                                                            30°F Activation Performance                                                          0°F Cold Performance                                                                 Reserve                                                                            Remarks                      centration                                                                          Days of                                                                            Prior                                                                              266 AMP Discharge                                                                           355 AMP Discharge                                                                           Capacity                          in Rinse                                                                            Storage                                                                            to Act-       Time to       Time to                                                                            Minutes                           Acid  at 110°F.                                                                   ivation                                                                            5sec.V.                                                                           15sec.V.                                                                           7.2V sec.                                                                          5sec.V.                                                                           30sec.V.                                                                           7.2V.sec.                              __________________________________________________________________________    NaOH to                                                                             84   11.22                                                                              Battery cut open to determine sulfation                                                                        Some sulfate bead or                                                          crystal                      yield                                            growth in the bottom of                                                       the                          0.5% Na.sub.2 SO.sub.4                           positive plate grid                                                           frame bar.                                                                    Not resulted in shorting                                                      yet                          82          8.41                                                                              7.52                                                                              7.50 50   7.81                                                                              7.62 77.0 120  Exhibited varying                                                             degrees of                                                                    sulfation from cell to                                                        cell in                                                                       the same battery. After                                                       activa-                                                                       tion, acid gravity                                                            varied from                                                                   1.205 to 1.250               KOH to                                                                              84  11.32 Battery cut open to determine sulfation                                                                        Sulfate deposit --                                                            randomly on                  yield                                            positive plate               0.4% K.sub.2 SO.sub.4                                                         82        11.00 7.98                                                                              7.98 74   7.92                                                                              7.77 82.0 121  Exhibited varying                                                             degrees of                                                                    sulfation from cell to                                                        cell in                                                                       the same battery. After                                                       activa-                                                                       tion, acid gravity                                                            varied from                                                                   1.197 to 1.247               ZnO to                                                                              84   9.81 Battery cut open to determine sufation                                                                         Sulfation of positive                                                         plate and                    yield                                            frame bars                   0.3% ZnSO.sub.4                                                                               150 AMPS                                                      82         7.80 --  8.50 188  7.79                                                                              7.60 74.0 132  Exhibited varying                                                             degrees of                                                                    sulfation from cell to                                                        cell in                                      Failed at 266 Amps               the same battery. After                                                       activa-                                                                       tion, acid gravity                                                            varied from                                                                   1.215 to                     __________________________________________________________________________                                                     1.245                    

EXAMPLE 11

Various capacity, plastic heavy duty, six volt batteries, typically usedfor golf carts, and having separators with glassmat backs, were formedusing a sulfuric acid aqueous 20 hr. formation. About 0.5% by weight ofsodium sulfate was added to the rinse acid (specific gravity - 1.347).After inverting and dumping to remove the rinse acid (about 50 to 60volume per cent of the acid being retained due to the porous type ofseparators used), the cover vent openings were substantially sealed asdescribed in Example 8; and the batteries were stored at temperaturesranging from 72° to 110°F. for from 61 to 302 days.

After opening the cover vent openings, electrolyte was added; and thebatteries were evaluated. The results are shown in Table X:

                                      Table X                                     __________________________________________________________________________    Battery                                                                            Reaction Time                                                                           No. of Days and                                                                         Open Circuit                                                                          Status of Battery and                        Type with Rinse Acid                                                                         Temperature of                                                                          Voltage Observations                                      in Minutes                                                                              Storage                                                        __________________________________________________________________________    220 AH                                                                             40        61 days - 110°F                                                                  3.88    No sulfate crystals were observed                                             on the positive plates. Internal                                              shorts were absent. Separators                                                were in good condition                       220 AH                                                                             40        61 days - 110°F                                                                  4.85    Retained 57.0% of the original                                                capacity following storage.                                                   Battery regained its rated                                                    capacity in subsequent cycling.                                               Battery okay on Life Cycle test              220 AH                                                                             40        302 days - 82°F                                                                  3.23    Retained 34.0% of the original                                                rated capacity following storage.                                             Battery regained its rated                                                    capacity in subsequent cycling               180 AH                                                                             10        139 days - 110°F                                                                 3.69    Retained 39.0% of the original                                                rated capacity following storage;                                             battery regained its rated                                                    capacity during subsequent cycling           180 AH                                                                             20        131 days - 110°F                                                                 5.58                                                 180 AH                                                                             20        131 days - 80°F                                                                  5.93                                                 180 AH                                                                             20        131 days - 72°F                                                                  5.99                                                 180 AH                                                                             30        131 days - 110°F                                                                 5.58                                                 220 AH                                                                             10        131 days - 110°F                                                                 5.38                                                 220 AH                                                                             20        131 days - 110°F                                                                 5.31                                                 220 AH                                                                             20        131 days - 80°F                                                                  5.89                                                 220 AH                                                                             20        131 days - 72°F                                                                  5.94                                                 220 AH                                                                             30        135 days - 110°F                                                                 3.24    Retained 35.0% of the original                                                rated capacity following storage;                                             battery regained its rated capacity                                           during subsequent cycling                    __________________________________________________________________________

Thus, as has been seen, the present invention provides a novel lead-acidstorage battery which can be stored for extended periods of time and iscapable of being activated by the addition of electrolyte, serving as areplacement for conventional dry charge batteries. The invention furtherprovides a drain dry process for forming such batteries which obviatesthe necessity for drying the battery to remove all the residualformation electrolyte or using relatively complex techniques such ascentrifuging to remove most of the electrolyte. Adequate electrolyte isremoved simply by draining. The process is versatile and may be usedeven with batteries whose elements retain up to 50 or 60 volume per centof the acid added.

As is apparent from the description provided herein, the conditioningtreatment in accordance with the present invention serves to protect thebattery during storage from the growth of crystals and clusters ofcrystals which can bridge between adjacent positive and negative platesto create internal shorts, thereby irreversibly damaging the battery. Itis this problem which has dictated, prior to this invention, the removalof at least substantially all of the electrolyte before storage in drycharge or dry charge-type batteries.

While it is not fully understood how the conditioning step of the draindry process of this invention functions to so protect the batteryelements, it is theorized that the kinetics and the morphology of theproducts of the chemical and electrochemical reactions that take placeduring storage are altered. During storage, due to the self discharge ofthe positive plates by sulfation occurring at a more rapid rate than atthe negative plates, a condition not occurring in a wet battery, acidgradients are created.

It is accordingly hypothesized that, as can be seen from FIGS. 2 and 3,the conditioning treatment of the soluble metal sulfate decreases thesolubility of lead compounds in the residual electrolyte solution in thebattery and maintains substantially the same solubility of the leadcompounds during the critical periods as the sulfuric acid is consumedby reacting with the active materials on the plates, forming leadsulfate and increasing the pH of the electrolyte up to a neutral level.The low solubility achieved at the initial acidic pH levels alters thekinetics of the crystal growth, and the maintenance of substantiallythis same solubility level during the entire course of pH changeprevents precipitation of the lead sulfate or other compounds that wouldotherwise occur at interfaces created between the acid gradients, whichprecipitation is thought to accelerate the growth of crystals orclusters of crystals that lead to the undesirable bridging between theplates.

We claim as our invention:
 1. A lead-acid storage battery comprising acontainer having a plurality of cell compartments and a plurality ofbattery elements consisting of a plurality of positive and negativecharged plates with separators positioned therebetween disposed in thecell compartments, said battery being sealed to at least substantiallyprevent the ingress of air and said battery elements containing aconditioning amount of a metallic sulfate and residual electrolyte andsaid battery being otherwise substantially free of electrolyte and beingactivatable by addition of electrolyte thereto.
 2. The lead-acid storagebattery of claim 1 wherein said metallic sulfate is sodium sulfate.
 3. Alead-acid storage battery comprising a container having a plurality ofcell compartments and a plurality of battery elements consisting of aplurality of positive and negative charged plates with separatorspositioned therebetween disposed in the cell compartments, said batterybeing sealed to at least substantially prevent the ingress of air andsaid battery elements containing residual electrolyte and a conditioningamount of a soluble metallic sulfate sufficient to prevent crystalgrowths and clusters extending between adjacent positive and negativeplates and said battery being otherwise substantially free ofelectrolyte and being activatable by addition of electrolyte thereto. 4.The lead-acid storage battery of claim 3 wherein said metallic sulfateis a sulfate selected from the group consisting of sodium, potassium,lithium, magnesium, cadmium, zinc, aluminum, silver, cobalt, beryllium,cerium, indium, lanthanum, tin, thallium, zirconium, rubidium andmixtures thereof.
 5. The lead-acid storage battery of claim 4 whereinthe metallic sulfate is sodium sulfate.
 6. The lead-acid storage batteryof claim 4 wherein the metallic sulfate is zinc sulfate.
 7. Thelead-acid storage battery of claim 4 wherein the metallic sulfate ispotassium sulfate.
 8. The lead-acid storage battery of claim 4 whereinthe metallic sulfate is lithium sulfate.
 9. The lead-acid storagebattery of claim 4 wherein the metallic sulfate is magnesium sulfate.10. The lead-acid storage battery of claim 4 wherein the metallicsulfate is cadmium sulfate.
 11. The lead-acid storage battery of claim 4wherein the metallic sulfate is aluminum sulfate.
 12. A lead-acidstorage battery comprising a container having a plurality of cellcompartments and a plurality of formed battery elements consisting of aplurality of positive and negative charged plates with separatorspositioned therebetween disposed in the cell compartments, said batterybeing sealed to at least substantially prevent the ingress of air andhaving been drained of electrolyte, said battery elements containing aconditioning amount of a metallic sulfate and residual electrolyte andsaid battery being activatable by addition of electrolyte thereto.